I’m pretty sure the explicit sync fix requires the 555 beta version of the Nvidia driver to be installed, as there’s a driver component that’s required.
What distro are you on? If it has a decent way to install the 555 beta that would probably be a good route to go with - but otherwise, no, switching to X11 shouldn’t require reverting any settings at all. I used to switch between the two sessions all the time, right before you enter your password on the login screen (you have to be completely logged out, not just at the screen lock) click the menu at the bottom right and it should have a “Plasma (X11)” option.